The book which Charles Faulhaber has in mind is the Epistolae
Obscurorum Virorum. It is my recollection, though it could be wrong, that
in this satire against the Scholastics composed by German humanists,
angels dance on pinheads. Pope refers to the Epistolae Obscurorum Virorum in
the prose sections of the Dunciad Variorum. It is mentioned in a prose
satiric advertisement to the 1742 edition where he thinks of his critics as
"obscure men". He associated it with satires of knowledge such as
Erasmus' Encomium Moriae. It obviously inspired some of the satire in
Memoirs of Martinus Scriblerus where as a previous comment suggests there
is a satiric use of angels dancing on the head of a pin.